SU954887A1 - Pulse train frequency measuring device - Google Patents

Description

The invention relates to automation and information-measuring equipment and can be used to measure the frequency with the issuance of the measurement result in digital form, suitable for input into an electronic digital computer 5.

A device is known for measuring frequency with increased counting speed and with high measurement accuracy, comprising a coarse frequency meter, ¹⁰ measuring an integer number of periods of the measured frequency, and a precision counter measuring the fractional part of the period of the measured frequency of the SP. ''

The closest in technical essence to the proposed one is a device for measuring the pulse repetition rate, containing a ₂ θ pulse generator of a reference frequency, a control trigger, two selectors, a frequency divider, a fractional part of the period of the measured frequency C2].

The disadvantage of this device is the need for a precision counter, with which there is a correction (refinement) of the measurement interval. In addition, the algorithm for calculating the measured frequency, requiring a subtraction operation, is complicated. All this leads to a complication of the meter circuit and to a deterioration in the reliability of the circuit as a whole.

The purpose of the invention is to increase the reliability of the device.

This goal is achieved in that in a device for measuring the pulse repetition rate, containing two selectors, a frequency divider, a counter, a control trigger, a reference frequency generator, the output of which is connected to the input of the first selector, the output of which is connected to the input of the frequency divider, and the control input of the first the selector is connected to the output of the control trigger and control- ³ <equal to the input of the second selector, the input of which is connected to the input bus, and the output of the second selector is connected to the input of the counter, two additional villages are introduced: a vector and an additional trigger, the input of which is connected to the output of the frequency divider, the output - with the first input of the first additional selector, and the inverse output of the additional trigger - with the first input

954887. 4 of selector 8, simultaneously closing the second additional selector 9. Another pulse of the measured frequency passes through the first additional selector 8 and enters the second input of trigger 2 of the control, putting it into Stop state, in which the first and second selectors 3 and 4 are closed.

According to counter 6, the second additional selector can be updated, the second input of which is connected to the second input of the first additional selector, to the input bus, to the input of the second selector, and the output of the second additional selector is connected to the first input of the control trigger, the second input of which is connected to the output of the first additional selector.

The drawing shows a block diagram of a device.

A device for measuring the pulse repetition rate comprises a reference frequency generator 1, a control trigger 2 25, a first selector 3, a second selector 4, a frequency divider 5, a counter 6 ,. additional trigger 7, first and second additional selectors 8 and 9. ₃₀

The device operates as follows.

The frequency measurement starts after zeroing the divider 5, the coarse counter 6 and the additional trigger 7 (zeroing chains are not shown in the drawing ³⁵ ).

The pulses of the measured frequency are fed to the input of the selector 4 and to the second inputs of the additional selectors 8 and 9.

The first pulse of the measured frequency passes through the second additional selector 9 and puts the trigger 2 control in the Start state, in which the first and second selectors 3 and 4 open. The counter 6 begins to pass pulses of the measured frequency, and the divider 5 ~ pulses of the reference frequency from the generator 1.

The filling of the divider 5 and the counter 6 ⁵⁰ starts at the same time (with an accuracy of one period of the reference frequency).

After a time T _o , determined by the capacity n _{0 of the} counter of the divider 5, the additional tribrach 7 is set ⁵⁵ to state 1 by the pulse from the output of the divider 5 and gives permission to the control input of the first additional ₍ determine the number N _{x of the} periods of the measured frequency f _x during the measurement time T _x Time measurements, on the one hand, is equal to Νχ periods of the measured frequency15 Τχ, i.e.

'Τχ = -ίΚ · ^(r O x

On the other hand, the measurement time is η _{χ of the} periods of the reference frequency 20 ^ et 'recorded on the counter of the frequency divider 5 and with the help of an additional trigger 7, i.e.

Tx = -Px- (2) ^g et

The number η _x periods of the reference frequency contains the number n ₀ periods of the reference frequency (at the time of overflow of the counter of the frequency divider 5) and the number of dp periods of the frequency f _3T (recorded on the counter of the frequency divider 5, at the moment of triggering of the control trigger 2), i.e.

n _x = η ₀ + yn. (3)

The number n ₀ is fixed using an additional trigger 7. The number dn is fixed in the counter of the frequency divider 5.

The measured frequency is equal to the ratio of the number of full periods of the measured frequency and their total duration, i.e.

f = ^Νχ = N * '^ ^et - f. N x _ * ^τ χ ^η Χ ^3Ύ n ₀ + dp

Thanks to the use of an additional trigger and two additional selectors instead of the Precision Counter ^, the meter circuit is simplified and the calculation algorithm is simplified, which leads to an increase in the reliability of the device.

Claims (2)

1. USSR Author's Certificate No. А82692, cl. 6 01 R 23/02, 1975. 2. Authors certificate of the USSR W 524139, cl. G 01 R 23/02, 1976 (prototype).